A number of metering valves are currently available in the market place. Most of these currently available metering valves utilize a ball or some other additional component which has to be separately installed in the valve housing to ensure proper metering of a desired quantity of an aerosol product from the valve assembly upon sufficient actuation or depression of the stem. The installation of this additional component, during manufacture of the aerosol valve, generally increases the production costs as well as the inspection costs associated with manufacture of the aerosol valve. Moreover, if the additional component is not properly installed or is omitted from the valve assembly for some reason, the aerosol valve will malfunction. Accordingly, an inspection step is generally required, following installation of the additional component, to confirm that the additional component was, in fact, properly installed within the aerosol valve.
Another drawback associated with prior art metering valves is that such valves have a tendency to “throttle”. That is, due to a poor or an improper valve design, it is possible for an operator to partially depress the valve stem and establish a product flow path from the interior cavity of the aerosol container through the metering valve and out through a spray button or an actuator affixed to the stem of the aerosol valve, prior to the valve stem sealing the inlet to the valve housing, so that product may be continuously discharged out through the aerosol valve. As a result of such “throttling”, the operator is able to dispense a continuous discharge of product from the aerosol container via the metering valve rather than meter a desired amount. This results in the inadvertent discharge of excess product from the aerosol container which is wasteful and generally to be avoided.
Another prior art design utilizes a frictional sealing fit between two plastic valve components to separate the contents of the container from the metering chamber. This arrangement requires that a valve spring, accommodated by the valve, be sufficiently forceful to overcome the interference fit of this sealing device upon the valve closing sequence. Apart from being subject to size and hardness changes due to immersion in the product, this design mandates extremely close tolerances of the mating components and critical alignment of molded parts during the valve assembly operation. Failure to observe these manufacturing tolerances and alignment criteria leads to an inaccurate metered spray or a valve which will not “shut-off” and thus result in the total release or dispensing of the entire product contents.